Key issues in Japan’s public health centers to prepare for future pandemics: a text mining study using a topic model

Background In Japan, over 450 public health centers played a central role in the operation of the local public health system in response to the COVID-19 pandemic. This study aimed to identify key issues for improving the system for public health centers for future pandemics. Methods We conducted a cross-sectional study using an online questionnaire. The respondents were first line workers in public health centers or local governments during the pandemic. We solicited open-ended responses concerning improvements needed for future pandemics. Issues were identified from these descriptions using morphological analysis and a topic model with KHcoder3.0. The number of topics was estimated using Perplexity as a measure, and Latent Dirichlet Allocation for meaning identification. Results We received open-ended responses from 784 (48.6%) of the 1,612 survey respondents, which included 111 physicians, 330 nurses, and 172 administrative staff. Morphological analysis processed these descriptions into 36,632 words. The topic model summarized them into eight issues: 1) establishment of a crisis management system, 2) division of functions among public health centers, prefectures, and medical institutions, 3) clear role distribution in public health center staff, 4) training of specialists, 5) information sharing system (information about infectious diseases and government policies), 6) response to excessive workload (support from other local governments, cooperation within public health centers, and outsourcing), 7) streamlining operations, and 8) balance with regular duties. Conclusions This study identified key issues that need to be addressed to prepare Japan’s public health centers for future pandemics. These findings are vital for discussions aimed at strengthening the public health system based on experiences from the COVID-19 pandemic. Supplementary Information The online version contains supplementary material available at 10.1186/s12913-024-11094-w.


Background
The novel coronavirus disease 2019 (COVID- 19) emerged as a threat to public health [1].The development and widespread adoption of treatment methods and vaccines have since reduced the mortality rate, and by May 2023, the World Health Organization declared an end to the public health emergency of international concern, indicating a shift towards crisis resolution [2,3].Japan likewise downgraded its disease handling protocol for COVID-19 from Class 2, including tuberculosis and SARS, to Class 5, including seasonal influenza, under the Act on the Prevention of Infectious Diseases and Medical Care for Patients with Infectious Diseases [4].In the preceding three years, nations globally fortified the functionality of their public health institutions in a bid to suppress the pandemic [5].
In Japan, public health centers, under the jurisdiction of the local governments, played a pivotal role in mitigating the pandemic's impacts [6,7].Even prior to the pandemic, these health centers were instrumental in sustaining local public health [8].Based on the Community Health Act of 1994, Japan had 469 public health centers in prefectures, ordinance-designated cities, and core cities in 2020 [9].Responding to infectious disease outbreaks was one of their many responsibilities for public health.The public health centers provided services such as infectious disease monitoring, HIV/AIDS and intractable disease management, mental health services, elderly health care, maternal and child health care, as well as food hygiene, sanitation, and medical care supervision [8,10].Additionally, these centers served as key response hubs during health crises, including natural disasters and infectious disease outbreaks [11,12].When infectious diseases, such as measles, rubella, and tuberculosis, emerged, public health centers swiftly responded [10].Therefore, from the early stages of the COVID-19 outbreak, these centers conducted epidemiological surveys, contact tracing, consultations for contacts and returnees from abroad, and managed the expansion and operation of PCR testing [13][14][15][16].As the infection spread domestically, their responsibilities expanded to include monitoring the health of home-care patients and coordinating their treatment in hotels or medical institutions.
The public health centers played a central role in the operation of local public health during this pandemic [17].As the pandemic's peaks arrived intermittently, the staff, particularly public health nurses, faced increasing burdens, leading to instances of depression and burnout [18,19].It has been reported that both a shortage of available human resources and inadequate support during the pandemic contributed to their exhaustion [19].The nearly three-year experience served as a lesson, prompting a reconsideration of the existing public health system in preparation for future pandemics.
To prepare for a potential resurgence of new infectious diseases, it is crucial to utilize the lessons learned from this pandemic to strengthen future responses.Several reports have attempted to review the current pandemic from governmental and expert perspectives [9,11].However, to our knowledge, there are no articles summarizing the issues that need to be addressed in future public health center systems from the viewpoint of those who have been directly responding to the pandemic at public health centers.In addition to expert reviews, it would be beneficial to collect a wide range of opinions from practitioners involved in the response and summarize discussion topics for the future public health center system.Hence, this study aims to identify and organize the issues that should be considered in preparation for future pandemic crises from practitioners' perspectives.

Study design
We carried out a cross-sectional study utilizing a questionnaire directed at workers in local governments and public health centers throughout Japan.The respondents were asked to provide unguided descriptions of the improvements needed in the future health center system, based on their response to the epidemic.To structure the issues for future discussion, we analyzed the descriptions using morphological analysis and a topic model in this study.

Selection of respondents in analysis
We recruited respondents via the managers of local governments and public health centers.We distributed letters of invitation to partake in the study to members of the Japanese Association of Health Directors of Prefectural Governments and the Japanese Association of Public Health Center Directors.We invited all managers of 468 public health centers, 47 local governments, and 20 government-designated cities, which covers all institutions in Japan, to participate in the study.The managers disseminated the invitation within their institutions, requesting workers to respond to the online questionnaire.The eligibility criterion for respondents was involvement in the COVID-19 pandemic response for at least six months as their primary duty.To collect a wide range of perspectives, managers were asked to encourage responses from individuals of various ages and professions, including physicians, veterinarians, public health nurses, medical nurses, other professionals, and administrative staff.We targeted approximately 10 respondents per institution to minimize the burden of response and to prevent response bias towards a few institutions.
Respondents completed the questionnaire by scanning a QR code or URL, which redirected them to a Microsoft Form.The response period spanned from December 2022 to January 2023.

Data collection
The online questionnaire consisted of questions regarding the characteristics of the respondents and public health center systems that should be discussed in preparation for the future.The questions related to the characteristics of the respondents were: sex (man, woman), age (20 s, 30 s, 40 s, 50 s, 60 +), length of continuous employment (0-5 years, 6-10 years, 11-15 years, 16 + years), occupation (public health nurse or midwife, doctor or dentist, other technicians, administrative staff ), job position (manager, non-manager), workplace (public health center, local government, other) areas of jurisdiction (47 prefectures).To collect text data in line with the purpose of this study, respondents were asked to provide an open-ended response to the following question: "Please describe any matters that you think need improvement in public health center operations for future pandemics."

Data analysis
We employed a text mining method to analyze the descriptions in three steps [20].
First, we performed a morphological analysis using ChaSen, a Japanese dictionary for text mining, to observe the 200 most frequently used words.To gain a comprehensive understanding of the descriptions, we also read all responses containing each word.
Second, we analyzed the descriptions using the topic model.A Topic model in text mining refers to the process of identifying key themes within a large body of text.This is typically achieved using statistical methods to analyze words and their frequency in a document, generating topics that signify the main themes present in the text.The number of topics was determined using perplexity, a measure of the model's predictive performance [21].In general, the lower the perplexity score, the better the model is considered.In this study, we used Latent Dirichlet Allocation for semantic interpretation, thereby identifying meaningful topics within our text corpus [22].Through this approach, we were able to reveal hidden thematic structures, aiding in a more profound understanding of our data.
Third, based on the results of the topic model, we conceptualized and structured the issues to be discussed about the future health center.In the process of structuring, we observed the words in each topic and the actual descriptions in which they were frequently used.
For our analysis, we used the freely accessible text mining software, KH Coder 3.0, developed by Higuchi from Ritsumeikan University, Kyoto, Japan (https:// khcod er.net/) [23].The choice of this software was influenced by numerous successful instances of its usage in public health-related text mining studies [24,25].Alongside this, we utilized the ChaSen Morphological Analyzer, a Japanese dictionary for text mining, and the R statistical software environment for our analysis.

Ethics
The study was structured to ensure that respondents reviewed and understood the guidelines about the study's aim, significance, methodology, measures for personal information protection, and potential risks before proceeding to the questionnaire.The questionnaire was designed to be anonymous, reducing the risk of data leaks, and to enable respondents to freely express their honest opinions.Thus, the aim was to secure their understanding and consent before response, while ensuring the integrity of their responses and personal data.
This study adhered strictly to the principles of the World Medical Association Declaration of Helsinki and received approval from the University of Occupational and Environmental Health, Japan's Ethics Committee (R4-042).

Characteristics of respondents
The characteristics of the respondents are presented in Table 1.Of the 784 respondents, 494 (63.0%) were women.Respondents in their 40 s and 50 s comprised over 50% of the respondents.More than 50% of the respondents had worked continuously for more than 16 years.Conversely, 181 (23.1%) had been working for less than 5 years.Public health nurses and midwives accounted for 330 (42.1%), and managers for 285 (36.4%).Workplaces were public health centers for 662 (84.4%) and local governments for 114 (14.5%).Jurisdictions were spread across the country.

Morphological analysis
In the first step, a morphological analysis of the descriptions was conducted.In total, 36,632 extracted words and 3,075 unique words were identified.We set public health center(hokenjo), public health nurse(hokenshi), occupational physician(sangyoi), COVID-19(korona), and medical institution(iryou-kikan) as specific words that frequently occurred in this study and were not included in Chasen.The 50 most frequent words and their occurrence counts are shown in Table 2.These included operation, manpower, coordination, outsourcing, hospitalization, information, regular duties, survey, and policy.

Topic model analysis
The results of the simulations for identifying the number of topics are shown in Fig. 1.We established the number of topics as 20.Table 3 displays the word sets that depict each topic when 20 topics were assigned.We interpreted the descriptions in which the word sets classified in each topic were frequently used and identified the issues raised by these descriptions.

Conceptualization of discussion issues
We could summarize the descriptions into the following eight issues; 1) establishment of a crisis management system, 2) division of functions among public

Discussion
In our study, we identified following eight issues for the future pandemics: establishment of a crisis management system; division of functions among public health centers, local governments, and medical institutions; clear role distribution in public health center staff; training of specialists; information sharing system; response to excessive workload; streamlining operations; balance with regular duties.We were able to discover comprehensive issues that are not only internal to the public health center, but also external to related agencies.
In a crisis, it is first necessary to recognize that the situation is critical and to affirm that the situation differs from normal circumstances.This concept is addressed in the first issue: the establishment of a crisis management system.The same issues are raised for medical response to disasters, which are based on seven principles: command and control, safety, communication, assessment, triage, treatment, and transport, known by the initial abbreviation CSCATTT [26].Among the eight key issues, both "Establishment of a crisis management system" and "Division of functions among public health centers, local governments, and medical institutions" pertain to command and control.Similarly, "Clear role distribution in public health center staff" is related to communication, while "Response to excessive workload" and "Balance with regular duties" are indicative of triage.Considering the similarity of the issues, leveraging existing disaster medicine frameworks and strategies could be useful in considering specific solutions for handling future pandemics.The pandemic placed an overwhelming strain on public health centers [17].Previous studies, like our own, have indicated that public health workers were forced to work long hours, with some required to be on-call at all hours, including nights and weekends.The lack of manpower prevented public health nurses from performing their regular duties such as supporting activities to prevent child abuse and neglect [27].Despite attempts to increase the number of staff, securing full-time public health nurses proved challenging, resulting in an increase in part-time staff who couldn't play a central role [28].As highlighted in our study, the training and retention of specialists are crucial factors in pandemic response.Studies have shown that areas with a high number of public health nurses before the pandemic had fewer infections [29].Securing human resources prior to an epidemic could be a crucial issue.
Beyond maintaining a system for normal operations, it is important to be prepared to organize people flexibly during a pandemic.It has been reported that during the pandemic, public health nurses in local governments helped to address the shortage of manpower in public health centers [30].Given the financial constraints of maintaining sufficient human resources under normal circumstances, temporary support will be necessary.The establishment of a crisis management system, as raised in this study, has already begun in some places.In Japan, the Infectious Disease Health Emergency Assistance Team (IHEAT) system has been set up to provide external resources for public health centers.IHEAT is a system in which public health nurses and other professionals in the community support the work of public health centers during health crises, such as the spread of infectious diseases [31].This project, which began during the pandemic, was formalized in the revision of the Community Health Law in April 2023.As a result, local governments that have established public health centers are now responsible for securing a support system with IHEAT personnel.For the future, we will need to prepare for a cooperative system that is tailored to the local circumstances.
Streamlining operations is also needed to reduce overwork during a pandemic.Numerous solutions that do not rely on human intervention, such as digital tools for epidemiological surveys and consultation services, have been developed during the pandemic [32][33][34].
COVID-19 led to a significant issue about infodemics due to the abundance of mixed information, which became a major public health issue [35].In this study, some respondents stated difficulties in handling numerous phone calls from residents.Additionally, the changing nature of the infection situation compounded this challenge, as new government guidelines were frequently issued, leaving public health workers in a difficult    The figures in the topic refer to numbers in Table 3 situation with uncertainty about the latest information [6].Implementing effective information sharing systems, especially about the government policy, would be useful in managing infodemics.

Strengths and limitations
One significant strength of this study is that it was able to consolidate the issues that need to be addressed for the future health center system based on the opinions of a wide range of frontline workers.Our study included individuals working in local governments and public health centers across the country, which provided us with a variety of perspectives.Past studies have had limited generalizability, as most were conducted in a few public health centers and mainly involved public health nurses [9,17].Furthermore, the application of a topic model in our analysis added a level of objectivity to the interpretation by researchers.
However, this study also has limitations.The first limitation is in its representativeness.When we recruited respondents for the survey, we asked all public health centers and local government managers to cooperate with us to collect as many respondents as possible.The managers who agreed to cooperate then encouraged cooperative people in their facilities to respond.Therefore, it is possible that there was sampling bias, leaning toward groups who were supportive of the study or who had many requests for improvements in their management.We note that the characteristics of the respondents were not representative of the workers who responded to the pandemic.The second limitation involves verification of the reported information in the open-ended questions.We designed the anonymous questionnaire so that respondents could freely express their opinions.As a result, we were not able to verify the accuracy of the descriptions provided.Although this study successfully identified key issues in preparing for future pandemics, it underscores the need for more objective future surveys.Such a survey would help in effectively determining the prioritization and resolution of these identified issues.The third is the inherent subjectivity involved in the researchers' interpretation of the data.Given the necessity of interpreting the responses when structuring them, we couldn't achieve wholly objective structuring.However, this study mitigated this effect by using a topic model to identify notable responses and cross-verifying actual responses with co-authors.

Conclusions
In contemplating the future of the public health center system, our findings suggest eight pivotal issues that warrant further discussion.Leveraging the experience accumulated during the pandemic to fortify the public health system will be essential moving forward.

Fig. 1
Fig. 1 Relationship between the number of topics and perplexity

Table 1
Characteristics of respondents

Table 2
Top 50 frequent words and their number of occurrences health centers, prefectures, and medical institutions, 3) clear role distribution in public health center staff, 4) training of specialists, 5) information sharing system (information about infectious diseases and government policies), 6) response to excessive workload (support from other local governments, cooperation within public health centers, and outsourcing), 7) streamlining operations, and 8) balance with regular duties.Table4lists these eight issues, the word sets of each topic that suggest these issues, and some representative descriptions from the respondents.

Table 3
Topic numbers and words extracted from open-ended questionnaire responses 18 Manpower, Deployment, Improvement, Need, Feel, Awareness, Especially, On-site, Infectious disease, Review 19 Need, Infectious disease, Municipality, Work, New type, Securing, Medical institution, Information, Outbreak, Many 20 Operation, Public health center, Local government, Collaboration, Many, Improvement, Role, Need, Securing, Outbreak

Table 4
Discussion points for considering improvements to the infectious disease pandemic with a focus on public health centers